1. Field of the Invention
The present invention generally relates to a microfluidic control device and method for controlling the same, and more particularly, to a microfluidic control device and method for controlling the same, which allows a pressure barrier to be removed by means of a surface tension change resulted from solution drop, thereby enabling transport, confluence, mixing, and time delay of the microfluid.
2. Discussion of Related Art
In order to configure a bio chip, a bio sensor, a chemical sensor and so forth for a biochemical analysis, a complicated fluid network for microfluidic control such as transport, stop, mixing, reaction, exchange and confluence, a valve capable of operating in a chamber, a pump, and so forth are required. To that end, various driving methods are proposed, for example, mechanical pumping, thermopneumatic pumping, an electrostatic actuation, an electrophoretic method, electrochemical actuation, and a capillary flow method by means of surface tension.
The microfluidic control device using the above-mentioned principles are classified into an active microfluidic component and a passive microfluidic component, wherein the active microfluidic component controls fluid employing a micro pump or a valve driven by electrical and mechanical external forces, and the passive microfluidic component uses natural force and controls the fluid by means of surface modification of geometrical manipulation of the flow path or chamber.
The microfluidic control device using the capillary force is the passive type component, which enables various control of fluid by means of natural attractive or repulsive force resulted from surface tension between fluid and inner surface of the micro-channel. In general, it needs not a driving means, so that additional power supply is not required, which allows a instrument including a bio chip to be small size, and fabrication and operation costs to be reduced, and it is hardly out of order.
One example of applying the surface tension to a micro system is disclosed in a Paper of Sensors and Actuators B 71 (2000) entitled to “Utilization of surface tension and wettability in the design and operation of microsensors”, wherein a pressure sensor, an accelerometer, a micro-pump, a micro-motor, fluid transport, fluid filling, inkjet, a robot probe, MicroOptoElectro Mechanical System (MOEMS) equipment, an optical shutter, a micro-switch, a micro stop valve, and so forth may be exemplified.
Examples of microfluidic control devices employing active control of fine droplet in the capillary are disclosed in U.S. Pat. No. 6,375,817 entitled “apparatus and methods for sample analysis” and U.S. Pat. No. 6,193,471 entitled “pneumatic control of formation and transport of small volume liquid samples”, respectively.
Typical examples of the microfluidic control device employing the capillary flow are disclosed in U.S. Pat. No. 6,271,040 B1 (7 Aug., 2001) entitled “Diagnostic Devices Method and Apparatus for the Controlled Movement of Reagents without Membranes”, U.S. Pat. No. 6,296,020 B1 (2 Oct., 2001) entitled “Fluid Circuit Components Based upon Passive Fluid Dynamics”, and U.S. Pat. No. 6,143,248 (7 Nov., 2000) entitled “Capillary microvalve”, and U.S. Pat. No. 6,130,098 (10 Oct., 2000) entitled “Moving microdroplets”.
The U.S. Pat. No. 6,375,817 discloses an apparatus for transporting and separating a fine amount of fluid in a fast automated manner by using mechanically generated pressure difference, however, it requires an additional device for generating mechanical pressure difference.
The U.S. Pat. No. 6,193,471 discloses an apparatus for generating, transporting, mixing fine droplet, and removing an air bubble by means of pneumatic pressure control of a multichannel, however, it also requires a device for generating the pneumatic pressure.
The U.S. Pat. No. 6,271,040 B1 discloses a bio chip structure for diagnosis, which transports sample only using flow resulted from capillary force and increases transport time using pressure increase of the structure while the samples are subject to reaction in a chamber, and determines whether the samples react with an optical method, however, its structure is complicated, which causes it difficult to fabricate the structure and to control reaction time.
The U.S. Pat. No. 6,296,020 B1 discloses a structure, which allows fluid to be stopped using hydrophobic material or sudden expansion of flow path in the capillary.
The U.S. Pat. No. 6,143,248 discloses a microvalve for transporting a fine amount of fluid from a micro storage chamber to a transfer chamber by controlling capillary and centrifugal forces, however, it should disadvantageously apply the centrifugal force so as to perform reflow after the fluid is stopped.
The U.S. Pat. No. 6,130,098 discloses a microfluidic device for transporting a predetermined amount of small volume fluid by means of thermo-pneumatic pressure and stop valve with hydrophobic surface, however, it requires an additional structure for pumping and high power consumption.
As mentioned above, additional mechanical device or electrical device is used to control fluid in the related art, which cause its configuration to be complicated and fabrication cost to be increased. In addition, complicated flow path should be changed or its surface treatment should be performed when the fluid needs to be stopped or its speed needs to be reduced.